In the early twentieth century, Fritz Haber discovered that was possible to produce ammonia with the use of catalysts such as iron, ruthenium, and osmium, and by fixing nitrogen from air at high pressure and moderate temperatures. The current world population is just above 7 billion, of which 3-3.5 billion would not exist without this process of ammonia synthesis, commonly referred to as the Haber-Bosch process. This process consumes approximately 2.5% of the world's energy needs.
The abatement of CO2 from point sources such as coal-fired power plants through the design of cost-effective membrane materials would decrease CO2 emitted into the atmosphere. Climate change will impact agriculture and food production around the world because of elevated CO2 in the atmosphere, higher temperatures, altered precipitation and transpiration regimes, and increased frequency of extreme events. With atmospheric CO2 concentrations increasing from 280 to 391 ppm since the start of the Industrial Revolution, it is imperative that new technologies are advanced to avoid prolonging business-as-usual activity.
When fuel oxidation was first carried out for energy generation, there was no intention of capturing the CO2 generated from the process. Air, the primary source of fuel oxidation, is approximately 78% N2 and 21% O2 by volume on a dry basis, excluding moisture content. N2 is predominantly an inert gas throughout the combustion process, thereby diluting the CO2 generated in the flue gas stream and increasing the work required for CO2 separation. Advanced coal conversion processes—such as coal gasification, oxycombustion, and chemical looping combustion—are under development to reduce the work required for separation by creating CO2-concentrated gas outlet streams. However, current state-of-the-art technology for air separation at the scale required for these advanced conversion processes is cryogenic distillation, which is very energy-intensive. The O2 requirements for these applications range between 3.0 to 20 tons/day/MW, which represents a significant potential market for O2 within a CO2 capture context.